java - 使用数据库中的数据创建 JSON 数组

Question

我的数据库 rel_act 中的特定字段的值存储为 1234,5678,9112我通过映射数组“rslt”读取这些值，因此当我将它们读取为

我希望以特定格式创建一个 json 对象

“rel_act”:[{“ref”:“1234”}，{“ref”:“5678”}，{“ref”:“9112”}]

请指教

谢谢

Answer 1

您可以对 JDBC 代码使用一个简单的包装器:(请注意，本示例中未包含 SQL2JSON.convertDateToString() 方法，请将其删除或添加您自己的方法)

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
/**
 * Creates a JSONARRAY from an java.sql.ResultSet.
 * @author Aries
 *
 */
public class SQL2JSON 
{

    public static JSONArray convert(ResultSet rs) throws SQLException, JSONException
          {
            JSONArray json = new JSONArray();
            ResultSetMetaData rsmd = rs.getMetaData();
            rs.beforeFirst();
            while(rs.next()) {
                  int numColumns = rsmd.getColumnCount();
                  JSONObject obj = new JSONObject();

                  for(int i=1; i<numColumns+1; i++) {

                    String column_name = rsmd.getColumnLabel(i);  //Bugfix , works better than getColumnName() /Aries 

                    switch( rsmd.getColumnType( i ) ) {
                      case java.sql.Types.ARRAY:
                        obj.put(column_name, rs.getArray(column_name));     break;
                      case java.sql.Types.BIGINT:
                        obj.put(column_name, rs.getInt(column_name));       break;
                      case java.sql.Types.BOOLEAN:
                        obj.put(column_name, rs.getBoolean(column_name));   break;
                      case java.sql.Types.BLOB:
                        obj.put(column_name, rs.getBlob(column_name));      break;
                      case java.sql.Types.DOUBLE:
                        obj.put(column_name, rs.getDouble(column_name));    break;
                      case java.sql.Types.FLOAT:
                        obj.put(column_name, rs.getFloat(column_name));     break;
                      case java.sql.Types.INTEGER:
                        obj.put(column_name, rs.getInt(column_name));       break;
                      case java.sql.Types.NVARCHAR:
                        obj.put(column_name, rs.getNString(column_name));   break;
                      case java.sql.Types.VARCHAR:
                        obj.put(column_name, rs.getString(column_name));    break;
                      case java.sql.Types.TINYINT:
                        obj.put(column_name, rs.getInt(column_name));       break;
                      case java.sql.Types.SMALLINT:
                        obj.put(column_name, rs.getInt(column_name));       break;
                      case java.sql.Types.DATE:
                        obj.put(column_name, SQL2JSON.convertDateToString(rs.getDate(column_name)));      break;
                      case java.sql.Types.TIMESTAMP:
                        obj.put(column_name, SQL2JSON.convertDateToString(rs.getTimestamp(column_name))); break;
                      default:
                        obj.put(column_name, rs.getObject(column_name));    break;
                    }
                  }

                  json.put(obj);
                }

            return json;
          }
}

这是一个如何调用它的示例。我正在使用自定义 MySQL 事务池和 JDBC SQL 句柄对象，但它应该可以修改为任何 JDBC 驱动程序对象(MySQL、Sybase、H2、HSQLDB、Oracle...)

import java.sql.ResultSet;
import java.sql.SQLException;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public synchronized JSONObject getCustomerReferences(int custID) {

            DBTransaction trans=null;
            TransactionPool transactionPool = null;
            JSONArray myArrayOfRefs= new JSONArray();
            JSONObject myObject = new JSONObject();


        try {
            transactionPool = TransactionPool.get();
            trans = transactionPool.beginWork();

            Map<String, Object> optionalParams = new HashMap<String, Object>();
            optionalParams.put("customerId", custID);


             String selectQuery ="SELECT orderId AS ref FROM table1 WHERE custId='[customerId]';" //with 'AS' you can customize your output to any JSON name
             JSONArray myArrayOfRefs = null;
             ResultSet rs = mySQLTransactionHandle.query(selectQuery, optionalParams);
             if(rs.next()) {
                 myArrayOfRefs =  SQL2JSON.convert(rs);
                 }

             //add JSON array to a JSON object 
             myObject.put("rel_act", myArrayOfRefs); //Add null check.

        } catch (Exception e) {
            e.printStackTrace(); //Add logging
       }
        finally
        {
             try {
                    transactionPool.commit(mySQLTransactionHandle);
                } catch (SQLException e1) {
                    e1.printStackTrace(); //Add logging
                }
        }
            return myObject;
        }